1. Field of the Invention
The present invention relates to a gear used widely in a power transmission mechanism of automotive vehicles, precise machines, industrial machines, components thereof and the like.
2. Description of the Related Art
In the related art, various ingenuities have been attempted on gears used in the power transmission mechanism of the automotive vehicles, the precise machines, and the like for enhancing the strength of teeth.
First Example of Related Art
FIG. 15 illustrates a gear in the related art as described above. In FIG. 15, a gear 100 has teeth 101 having arch-shaped curved surfaces 102 on the tooth bottom side, which are close to each other to an extent that does not interfere with a trajectory of motion of teeth of a counterpart gear (pinion) meshing therewith, and the position of a dangerous section in the Hofer's 30 degrees tangent method is moved from P1 to P2 toward a tooth tip side, whereby the strength of the teeth is enhanced (refer to Patent Literature 1).
Second Example of Related Art
A gear configured to enhance the strength of dedendums by forming a tooth bottom side area of a tooth right angle cross section into an oval shape is known (refer to Patent Literature 2)
Patent Literature 1: Japanese Translation of PCT International Application Publication No. JP-T-2004-519644
Patent Literature 2: Japanese Translation of PCT International Application Publication No. JP-T-2009-531613
However, in the gears according to the first and second examples of the related art, a stress variation width including a tensile stress and a compression stress generated in the tooth bottom side area is not considered, and the maximum stress amplitude portion caused by the stress variation width generates at a center of the tooth bottom or in the vicinity thereof, so that the durability of the tooth cannot be enhanced sufficiently.